So, your KMD-150 or Skyforce IIIC or
Tracker IIIC internal battery is Tango Uniform and are getting the failed
battery message and the unit does not remember where it was when it was last
shut down?

Did the avionics shop quote
you $250 or more to change it?

Well I hate to break this to you but that
battery is under $10! These units are circa 1999/2000 and my battery lasted 9
years. Many of these units still in use will be requiring this memory battery
replacement right about now.

Here's the info on how to find a source for the
battery and change it out.

You will want the battery with the "Axial"
connections, these are the wires pre-soldered onto the ends of the battery
(see battery pic above and below). This is usually -AX in the part number. You may
remove a battery marked 3.7 volts. My experience is that the 3.6 volt battery
works just fine.

Here are the guidelines (posted by Tom
B. at
Piper Owners Forum)
to do micro-surgery on your Skyforce unit to get at the battery. KMD150 is
different (see Beech owner pirep below) but not much more complicated:

Disclaimer: this operation is best performed by
someone with electronics expertise or at least that is comfortable with
electrical disassembly and pencil soldering. The battery is soldered directly
to the printed circuit board (PCB) and there are no provisions to isolate /
disable the battery while removing the old and soldering the new. If the
battery is installed backwards, the leads inadvertently touch an adjacent
component, static electricity, etc… your GPS will instantly become nothing
more than an expensive desktop paperweight.

Changing the battery itself is not
difficult, you just have to be aware, be comfortable using a pencil-type
soldering iron and make sure you do it right. If you are the least bit
squeamish, don’t chance damaging a great GPS. Buy the battery and take
everything to the local electronics shop or return it to the factory.

1. Place the GPS face-down on a thick piece of foam (to prevent damaging the
front panel toggle switch).

2. Remove the hex-head screws retaining the rear panel assembly.

3. Slowly separate the rear panel from the main chassis. This is a little
difficult because the interconnections (stake-pin connectors) between the PCBs
have a lot of retention force. Move one corner, then the other, etc and the
connectors will separate without bending the leads on the gold stake-pin
connectors.

4. After separating the rear panel assembly from the main chassis assembly,
disconnect the coax connection between the GPS receiver PCB (mounted on the
main chassis) and the rear panel assembly. Set the main chassis assembly
aside.

5. Carefully remove the PCB from the rear panel assembly. The battery is
located on the opposite side of this PCB.

6. Using an indelible pen, mark the + / - battery orientation on the PCB. This
is to aid you to install the new battery with the correct polarity. The
battery terminals are clearly marked with a + and – on the GPS.

7. Now it’s time to remove the old battery. If you sourced a new battery
WITHOUT the axial wires cut the old battery leads as close to the body of the
battery as possible, leaving the battery leads attached to the PCB. You will
use these leads to reattach the new battery later on unless you got the
battery with the wires already soldered. If you got the battery WITH the axial
wires on the end, simply unsolder the old battery wires from the PCB and pull
up (using needle nose or some other such tool) on the wire when the solder
becomes liquid. Carefully clip the excess wire below the PCB after you have
them soldered.

8. Now it’s time to install the new battery. Carefully orient the new battery
correctly and carefully lay it onto the PCB. Notes: Install the battery
backwards and its goodbye GPS. Let the battery leads touch an adjacent
component and its goodbye GPS. Get the idea?

9. Solder the – lead first, then the + lead. Don’t loiter, solder the lead and
remove the soldering iron. Too much heat will damage the battery, unsolder the
lead to the PCB and subject the circuitry to unnecessary static discharges.

Here are pics of the KMD-150 that my buddy
did surgery on to remove his TU battery. It's not rocket science, just careful
disassembly and a steady hand with a soldering pencil.

Here is a narrative contributed by fellow Beech
Lister and K35 Bonanza owner for the KMD150 battery replacement:

Well as luck would have it, the system battery on my KMD150
Display died. Each time you would activate the unit there would be a pesky
reminder that stored data would be lost. Nothing serious because I've never
taken advantage of any type of available storage, if it actually does exist.

A battery change is about $250.00 and King would probably have
to send it to England where there is only one fellow working all repairs on the
Skyforce and KMD150's. Been there, done that, 7 weeks and $600.00 for I don't
know what once. I figured if one monkey can do it, this monkey can do it better
and a lot cheaper. Using info obtained from CSOBeech.com, I decided to go for
it. Read and reread the Piper owner's narrative about how he replaced it in his
Skyforce and how difficult it was and not for the faint of heart. He stated that
he was an engineer so he had the capability to do it. This put me over the edge
because for a short while I worked for Conrail and was able to drive a
locomotive. Not far, but drive it I did so I figured I could try this. If I
screwed it up I could sneak up to Kevin's, pinch his and get a new database card
to boot. Life is good being a Democrat (or it will be soon!).

Okay, on to it! I realized that the Skyforce and KMD150 are
really and truly two different animals but they were both British and hey, I do
work on my Jag so here we go. After sliding the radio out and placing it on the
bench I gave it the once over and scanned how I could crack this safe.

Started by removing the top panel. Two stainless Allen head
screws around back. Next I popped off the bottom, similar securing devices. Now
you can see a few boards, some ribbon cables (which IMHO would be the weak point
- remember that Jaguar?) and some plugs. Next comes the screen overlay (4
countersunk Phillips head screws) with the controls which I place in an
antistatic bag but do not disconnect the ribbon, so it's still attached. Next,
the screen unit which gets the same treatment. The screen is held onto the side
chassis with 4 countersunk Phillips head screws and onto a bottom brace with 1
regular Phillips head screw. Side chassis are still attached. Now, since the
entire viewing end is swinging in the breeze, I really need to be careful.
Somewhere along the way I needed to remove a guide pin, held on by an Allen head
screw from inside the box.

Now I can see the battery. Yup, it's the same 3.6 volt Lithium
battery that you see on the CSOB site. About $4.00 and $10.00 shipping. At this
point I do not know how much juice it's still carrying, so I'm a bit
apprehensive about maneuvering about it with metal tools. Lots of mini circuitry
that could be damaged without you even knowing it. In order to retrieve the
battery, the first overlay board needs to be removed. Easier said than done
because there's a 9 pin plug hardwired in and screwed to the board. I elected to
only loosen the board up and move it out of the way, which was okay. I removed
the Phillips head screws (4) that held the board to the standoffs. Due to the
lack of any reasonable amount of room to work, I just clipped the battery wires
AT the battery, negative first, then positive and removed the battery. After
that I just unsoldered the wires from the board. All the screws were placed into
a container as they were removed and of course, the radio was on a rubber mat.
Incidentally, the battery measured .99v. Date stamp was 05/99.

At this point it was time to get a battery. This is something
that I highly recommend you have before you start the job, I didn't. By using
the CSOB guidelines, (this has been corrected to specify AXIAL) I first wound up
with the wrong battery configuration. You don't want "tabs" connected, you want
it configured as AXIAL, which means there is a solid wire on each end. "Tabs"
come through as flat pieces of metal that are solderable. If I didn't remove the
wire stubs from the board, I may have been able to solder them to the tabs but
that would really be Mickey-Mouse, something you would expect from an overpriced
avionics shop. So after two weeks of saying I'll never do this again, I get back
to the bench and start the reassembly, shaking my head all the way.

I start by cleaning out the holes in the board using a solder
remover. I tested the holes with the wire and had to open one up a bit with a
tiny circuit board bit. Next I cut the positive + side wire on the battery to
size and tried it. After a bit more trimming, I slid on some wrap and shrunk it
down, just like the part that was removed. Soldering was straight forward, I
used a battery powered iron that I've had good luck with on boards. Positive
first just in case it came into contact with another past of the circuitry, then
negative.

Let it cool and gave it the yank test. All was good!

Now to reassemble. Every screw had a white substance on it
that I figured was a chemical thread lock. Used a tiny bit of Locktite on all,
so I hope my guess was a good one. Back to the advice that you need to have a
battery before you start and make this a one sitting job. If you can't, digital
pictures and a log are a must to know which comes/goes first, the chicken or the
egg. Mine sat for two weeks before I got back to it. In two weeks I can easily
forget how high my tab is with Kevin O., so I had a bit of a struggle
which section to start with. After removing panels a few times to route those
lousy ribbons, it was back together and in the aircraft.

Turned it on and viola! it worked. We'll see how it fares as
again, I don't trust the ribbons.